Baking cake in one pan instead of splitting into two

That is highly unlikely to work in your case. Summing up all ingredients, I came to 1600 ml. I don't know what exact density cake has, but it is a foam full of air, so being twice as light as water seems plausible, which would make your single layer 3 inches high. And the pictures in the article pretty much agree with my guess, the cake pieces are 1.5 times as long as they are high.

If you try to bake a 3 inch high cake layer, there is basically no time and temperature at which you can get it baked, you will always end up with a raw middle or with dust-dry, if not burnt, outer portions.

If you insist making it a single piece, you may try a bundt pan instead of a cake pan. Alternatively, make half the recipe (assuming that your pan is indeed 9 inch - if it is 28 cm, you can make 2/3 of the recipe to get the same height) or really go with the two layers.

I wish I saw this earlier but I guess this can help anyone that may come across this, but you can bake it in the same pan, just make sure to but a boundary of baking paper around the inner perimeter of the pan in case it bakes taller than the height, and then bake it at a lower temperature so it doesn’t burn before it is completely baked. The lower temp would make it take longer, for example baking it at 125 Could take about 2 hrs so that's good to keep in mind.